The capacity for face processing is highly developed in species like primates that have complex social structures. Disorders of face processing like Autism, Williams Syndrome, and developmental prosopagnosia can profoundly affect social relationships and communication. In humans, some aspects of face processing develop quite early and are exhibited in very young infants. However, other aspects of face processing take much longer to develop and may not reach adult levels until adolescence or later. This protracted developmental timeline for face processing may depend on a variety of factors. Some aspects of brain morphology like myelination and white matter development also have a protracted developmental time course. These features of brain maturation may not reach adult levels until late adolescence or early adulthood. The present application explores the possibility that protracted development of face processing in humans is related to the development of specific functional and anatomical connections within the brain. Such developmental changes may support a neural system for social cognition that includes face processing. Non-human primates (NHPs) exhibit many of the same face processing capacities as humans, as well as some aspects of social cognition, making this species an ideal candidate for animal models of typical and disordered development of social cognition. However, it is not known whether large-scale brain networks for face processing are shared with humans. A comparative approach can help determine whether developmental changes in neural systems that support face processing are driven by the specific experiences of the human or whether such neural organization is present in other species, despite their very different experiences. To determine species similarity and divergence for face processing in the developing brain, this application will conduct functional and anatomical connectivity analyses in human children, adolescents and adults and in mature NHPs (macaca mulatta). This research plan will consist of two phases, an initial developmental phase (the R21 phase) that will focus on establishing and refining functional magnetic resonance imaging (fMRI;used for functional connectivity) and diffusion tensor imaging (DTI;used for anatomical connectivity) techniques in NHPs and a second R33 phase in which connectivity data from humans are collected and compared to the data in NHPs. The overall scientific goal is to characterize the large-scale anatomical and functional brain networks in humans and NHPs for the perception of faces and for the processing of emotions in the face. Both capacities are critical for highly social organisms but species-specific experiences may modulate these networks differently. One benefit of the proposed research is that the brain imaging techniques that will be used to characterize large-scale brain connectivity are non-invasive and may help guide more targeted but invasive approaches that use NHPs as an animal model for typical and atypical development. Overall, the findings from this application will advance our understanding of the primate brain basis for social cognition. Public Health Relevance: A better understanding of brain connectivity patterns for face processing in humans and non-human primates can help develop animal models of typical and atypical social development. Such findings can be used to target behavioral or pharmacological interventions for conditions like Autism Spectrum Disorder or Williams Syndrome.